1. The Field of the Invention
The present invention relates to compositions and methods for whitening and desensitizing teeth. The present invention relates to compositions that may be applied directly to a person's teeth for shorter periods of time, and those specifically formulated for use with flexible, thin-walled dental trays in order to provide prolonged treatment of a patient's teeth over longer periods of time.
2. The Relevant Technology
The use of certain foods and tobacco, the process of aging, diseases, trauma, medications, some congenital conditions, and environmental effects can cause teeth to become discolored. Because teeth without discolorations are usually considered to be aesthetically superior to stained or discolored teeth, there has been a heightened level of interest of late in developing compositions and methods for bleaching teeth.
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is slightly porous. The outer layer is the protective layer of the tooth. The natural color of the tooth is opaque to translucent white or slightly off-white.
Some dental compositions like dentrifices, toothpastes, gels, and powders contain active oxygen or hydrogen peroxide liberating bleaching agents. Such bleaching agents include peroxides, percarbonates and perborates of the alkali and alkaline earth metals or complex compounds containing hydrogen peroxide. Also, peroxide salts of the alkali or alkaline earth metals are known to be useful in whitening teeth.
The most commonly used dental bleaching agent is carbamide peroxide (CO(NH.sub.2).sub.2.cndot.H.sub.2 O.sub.2), also called urea hydrogen peroxide, hydrogen peroxide carbamide, and perhydrol-urea. Carbamide peroxide has been used by dental clinicians for several decades as an oral antiseptic. Tooth bleaching was an observed side effect of extended contact time. Over-the-counter compositions of 10% carbamide peroxide are available as GCIY-OXIDE.RTM. by Marion Laboratories and PROXIGEL.RTM. by Reed and Canuick. A bleaching gel which is able to hold a comfortable-fitting dental tray in position for an extended time period is available under the trademark OPALESCENCE.RTM. from Ultradent Products, Inc. in South Jordan, Utah. Other bleaching agents such as peroxyacetic acid (CH.sub.3 C.dbd.OO--OH) and sodium perborate, are also known in the medical, dental and cosmetic arts.
Patients who have desired to have their teeth whitened have typically done so by applying a bleaching composition to the teeth by means of a dental tray for repeated treatments, or they have had to submit to conventional in-office bleaching techniques that required from 4 to 10 visits to the dental office before clinically significant results were achieved. Clinically significant results are quantifiable such as by measuring gray scale, L*, and as to yellowness or blueness, b*, in the CIE.RTM. system of color measurement or by equivalent methods.
Patients expecting their teeth to be whitened by such bleaching treatments may be pleased to have their stains removed, however, a more ideal aesthetic objective of whiter teeth may still not be adequately achieved. The removal of stains and discolorations sometimes reveal that the stains camouflaged teeth which are excessively translucent. Depending on the degree of translucency, the teeth may be revealed to be overly grey or even have portions which appear to be more transparent than is desired.
Brushing teeth with toothpaste does not address the problem of excessively translucent teeth. Brushing teeth with toothpastes or polishes is also less effective for whitening teeth compared to the application of bleaching treatments. Tooth brushing is less effective for whitening teeth as brushing teeth only cleans the external surface of the teeth while bleaching addresses internal stains in the teeth.
From the foregoing, it will be appreciated that what is needed in the art are compositions and methods for opacifying and decreasing the transparency of teeth.
It will also be appreciated that what is also needed are methods and compositions for opacifying teeth and whitening teeth without causing teeth to become overly sensitized.
What are also need are compositions and methods which are able to bleach teeth while concurrently offsetting the tendency of bleaching agents to cause teeth to become overly sensitive.